1. Field of the Invention
The present invention relates to an ink jet printer for printing a printing medium by ejecting droplets of ink onto it. In particular, the invention relates to an ink jet printer including a drive mechanism for moving a print head carriage without vibration of the head and splipping of a driving belt for the carriage.
2. Description of the Related Art
A certain ink jet printer or another printer includes a print head, a carriage on which the head is mounted, and a mechanism, for moving the carriage, which includes a pair of toothed synchronous pulleys and a toothed timing belt running between the pulleys. The carriage is connected to the belt. While the carriage is moved over a printing medium, the head prints the medium. The belt has teeth formed on its overall inner periphery. The pulleys are a driving pulley and a driven pulley, each of which has teeth formed on its overall outer periphery. When the teeth of the pulleys and belt mesh, their interference generates vibration, which prevents the belt from turning smoothly. Particularly in the case of an ink jet printer for high resolution printing, this vibration is transmitted through the carriage to the print head, and affects the printing quality.
Japanese Utility Model Publication No. H.3-38515 discloses a toothed driving pulley, a toothless driven pulley and a half toothed belt. The belt includes a flat half for engagement with the driven pulley. This prevents the belt and the driven pulley from interfering, and therefore suppresses the generation of vibration. Because the teeth of the driving pulley and the belt mesh, however, it is not possible to avoid the vibration generated by the interference of the teeth during printing.
It is possible to further suppress the vibration generation by making the driving pulley also toothless and the whole belt flat without any teeth. By the way, a certain ink jet printer takes advantage of the movement of its carriage to control its maintenance mechanism for sucking ink from the print head and/or capping the head. During this movement, the load on the carriage is so great that, if both pulleys and the whole belt are toothless, the belt may slip on the pulleys.